From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751183AbdAPOsz (ORCPT ); Mon, 16 Jan 2017 09:48:55 -0500 Received: from mga05.intel.com ([192.55.52.43]:26311 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750874AbdAPOsv (ORCPT ); Mon, 16 Jan 2017 09:48:51 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.33,239,1477983600"; d="scan'208";a="49345760" Date: Mon, 16 Jan 2017 16:48:47 +0200 From: Jarkko Sakkinen To: James Bottomley Cc: tpmdd-devel@lists.sourceforge.net, open list , linux-security-module@vger.kernel.org Subject: Re: [tpmdd-devel] [PATCH RFC v2 3/5] tpm: infrastructure for TPM spaces Message-ID: <20170116144847.p7nh3vvmqdoqlq7y@intel.com> References: <20170112174612.9314-1-jarkko.sakkinen@linux.intel.com> <20170112174612.9314-4-jarkko.sakkinen@linux.intel.com> <1484270243.5807.31.camel@linux.vnet.ibm.com> <20170116090931.dzdv4tcvhj4m4rrl@intel.com> <1484576688.2540.18.camel@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1484576688.2540.18.camel@linux.vnet.ibm.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo User-Agent: Mutt/1.6.2-neo (2016-08-21) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 16, 2017 at 06:24:48AM -0800, James Bottomley wrote: > On Mon, 2017-01-16 at 11:09 +0200, Jarkko Sakkinen wrote: > > On Thu, Jan 12, 2017 at 05:17:23PM -0800, James Bottomley wrote: > > > On Thu, 2017-01-12 at 19:46 +0200, Jarkko Sakkinen wrote: > > > > @@ -189,6 +190,12 @@ struct tpm_chip *tpm_chip_alloc(struct > > > > device > > > > *pdev, > > > > chip->cdev.owner = THIS_MODULE; > > > > chip->cdev.kobj.parent = &chip->dev.kobj; > > > > > > > > + chip->work_space.context_buf = kzalloc(PAGE_SIZE, > > > > GFP_KERNEL); > > > > + if (!chip->work_space.context_buf) { > > > > + rc = -ENOMEM; > > > > + goto out; > > > > + } > > > > + > > > > > > I think the work_buf handling can be greatly simplified by making > > > it a pointer to the space: it's only usable between > > > tpm2_prepare_space() and tpm2_commit_space() which are protected by > > > the chip mutex, so there's no need for it to exist outside of these > > > calls (i.e. it can be NULL). > > > > > > Doing it this way also saves the allocation and copying overhead of > > > work_space. > > > > > > The patch below can be folded to effect this. > > > > Hey, I have to take my words back. There's a separate buffer for > > space for a reason. If the transaction fails for example when RM is > > doing its job, we can revert to the previous set of transient > > objects. > > > > Your change would completely thrawt this. I tried varius ways to heal > > when RM decorations fail and this is the most fail safe to do it so > > lets stick with it. > > That's why I added the return code check in the other patch: if the > command fails in the TPM, the space state isn't updated at all, the net > result being that nothing changes in the space, thus you don't need the > copy, because there's nothing to revert on a failure. You are right in what you say but what if you save lets say 5 transient contexts and ContextSave fails on 2nd. It's not for the command itself but for falling back to a sane state when tpm2_commit_space fails (to the previous set of transient objects). I've never meant it as a fallback for the command itself... > If you're thinking transaction being a sequence of TPM commands, then > we might need an ioctl to transfer the space state to/from userspace, > so it can do rollback for several commands, but that too wouldn't need > us to have a single prior command saved copy. > > James Here I refer to transaction as a single tpm_transmit. /Jarkko